Phillips has an older brother, Peter Phillips (born 15 November 1977) and two half-sisters, Felicity Tonkins (born in 1985 to her father by his brief affair with Heather Tonkins)[6] and Stephanie Phillips, born 2 October 1997 from her father's second marriage to Sandy Pflueger.

The children of the Princess Royal do not hold any royal or noble title. They are not entitled to royal status by right of birth, as they are the grandchildren of a monarch in the female line, and their father declined a title in his own right.[7] As a child she and her brother attended Trooping the Colour and a few other royal events with their mother.

On 8 July 2013, it was announced by Buckingham Palace that Phillips and Tindall were expecting their first child.[15] With her husband present, Phillips gave birth to a daughter, Mia (pronounced My-ya)[16] Grace Tindall, on 17 January 2014 at Gloucestershire Royal Hospital. She is 16th in the line of succession.[17] Phillips has hopes of raising her daughter to be athletic.[18] As Phillips herself is a public figure, appearances of her daughter are also often noted.[19] Contrary to rumour, she has not hired a nanny.[20] Mia was christened on 30 November 2014 at St Nicholas Church in the village of Cherington.[21]

Following in both her parents' footsteps, Phillips is an accomplished equestrian.[22] In June 2003, she announced that she had secured a sponsorship deal with Cantor Index, a leading company in spread betting, to help cover the costs of her equestrian career. Zara finished runner up at Burghley Horse Trials in 2003 in her and Toytown`s first four star event.

Despite winning team gold at the 2007 European Eventing Championships in Italy, she failed to defend her individual title after a problem in the show-jumping phase of the competition.[23]

The British Olympic Association announced that Phillips would be riding Toytown for the British equestrian team at the Beijing Olympic Games 2008 in Hong Kong.[24] However, an injury sustained by Toytown during training led to her being forced to withdraw from the team. Zara previously missed the 2004 Summer Olympics in Athens, when Toytown suffered a similar injury during training.[25]

On 25 October 2008, she fell from her horse, Tsunami II, at the 15th fence of a cross-country event at Pau, France, and broke her right collarbone. The horse broke its neck after it had tipped over the hedge and was put down.[26]

On 11 June 2012, Phillips was announced as being a part of the British Equestrian team at the 2012 London Olympic Games.[27] She competed in the 2012 Olympics on her new horse, High Kingdom, where she won silver in the team eventing. Her medal was presented by her mother, Princess Anne.[28] Philips finished 2nd at Luhmühlen Horse Trials 2013, on her top horse High Kingdom. At the World Equestrian Games in 2014 Zara and her top horse High Kingdom were part of the British team that won team silver.

Phillips supports many charitable causes. In 2003, she and her mother took part in the first UK double ship-naming ceremony in Southampton. The Princess Royal named the P&O Cruises liner Oceana, and Phillips named its sister ship Adonia.

She frequently attends various events for charity and has taken to supporting certain causes herself, mainly for spinal injuries, equestrian charities and children's causes. In 2005, she auctioned one of her evening gowns (worn at the London premiere of the film Seabiscuit) to raise money for tsunami relief. She also undertook a visit to New Zealand in her role as patron of The Catwalk Trust. From 1998 to 2005, she served as the president of Club 16-24, a group which encourages young people to take an interest in racing. She is linked to INSPIRE, the Salisbury based medical research charity which helps to improve the quality of life of people with spinal cord injuries, and Sargent Cancer Care for Children, the UK's leading children's cancer charity.

She appears at events for The Caudwell Charitable Trust, which is targeted at children with special needs, disabilities and serious illnesses. In 2006, she took part in a special charity day for Cantor Index, whose staff were killed in the 11 September 2001 attacks. In 2007, she became patron of the Mark Davies Injured Riders Fund.[29] To help with Sport Relief 2008, she posed for her first official royal portrait by artist Jack Vettriano.[30] In 2009, she attended a celebrity poker tournament in Monaco in aid of Darfur, Sudan.[31] In September 2010, she attended the 2012 London Olympic Ball alongside cousin Prince Harry of Wales. In October of the same year she attended another celebrity poker tournament, this time in London, in aid of Cancer Research UK, of which she is Royal Patron. In 2011 she auctioned another evening gown, this time in aide of the Christchurch, New Zealand appeal, with the gown raising £22,000. In 2012 she attended various events marking her grandmother's Diamond Jubilee, although she missed the flotilla due to her commitments with the 2012 Olympics. In 2013, she visited the Stroud Maternity Ward, where she gave birth in 2014, to celebrate their 60th anniversary. In the same year she attended the Chelsea Flower Show alongside her grandmother The Queen. In 2014, Zara lent her support to the #bringbackourgirls campaign that United States First Lady Michelle Obama started.

In 2009, it was announced that Phillips would be designing her own range of equestrian clothing for Musto Outdoor Clothing.[32][33] The range is named ZP176 after the team number Zara was given when she first represented her country. The range was officially launched in July 2010.[34]